The New Fluorescence Enhancement System Eu<Superscript>3+</Superscript>-ARADE-HMTM-Al<Superscript>3+</Superscript> and its Analytical Application

A new bis-Schiff base ligand, N,N-bis-(4-N-aminothiourea-2-amylidene)-4,4-diaminodiphenyl ether (ARADE), was synthesized. Its complex with Eu³⁺ in DMF emits the intrinsic fluorescence of Eu³⁺. The fluorescence intensity of the Eu³⁺-ARADE system was enhanced about 60-fold by the addition of hexamethylene tetramine (HMTM) and potash alum. This is a new fluorescence enhancement phenomenon. The excitation and emission wavelengths are 375nm and 615nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Eu³⁺ in the range of 7.8×10^–9–1.75×10^–5mol·L^–1 with a detection limit of 5.2×10^–9mol·L^–1, or with the concentration of Al³⁺ in the range of 3.1×10^–7–9.7×10^–5mol·L^–1 with a detection limit of 2.7×10^–7mol·L^–1. The interferences of some rare earth metals and other inorganic ions were described. This method was applied to the determination of Eu³⁺ in high purity yttrium oxide and the analysis of Al³⁺ in alloy steel standard samples. The mechanism of fluorescence enhancement was also studied.     

The outersphere complex of EuCl2+ in a mixed system of methanol and water of 1.0M (H, Na) (Cl, ClO4)

The stability constans, ₁, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm^–3 ionic strength using a solvent extraction technique. The values of ₁ increase with an increase in the mole fraction of methanol (X _S ) in the mixed solvent system when 0X _S 0.40. The, distance of Eu³⁺–Cl^– in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived from ₁. Calculation of the Eu³⁺–Cl^– distance and the preferential solvation, of Eu³⁺ by water proposed the variation of the outersphere complex of EuCl²⁺ as follows: (1) [Eu(H₂O)₉]³⁺Cl^–, [Eu(H₂O)₈]³⁺Cl^– and [Eu(H₂O)₇(CH₃OH)³⁺Cl^– inX _S0.014, (2) [Eu(H₂O)₈]^3–Cl^– and [Eu(H₂O)₇(CH₃OH)]³⁺Cl^– in 0.014<X _S <0.25 and (3) [Eu(H₂O)₇(CH₃OH)]^3–Cl^– and [Eu(H₂O)₆(CH₃OH)[₂ ³⁺Cl^– in 0.25<X _S 0.40.     

Radioluminescence of Europium(III) in POCl3–SnCl4–235UO2+ 2–Eu3+, and D2O–235UO2+ 2–Eu3+ Solutions

Results of studying the spectral and luminescent properties of Eu³⁺ ions upon homogeneous excitation of POCl₃–SnCl₄–^-UO²⁺ ₂–Eu³⁺ and D₂O–²³⁵UO²⁺ ₂–Eu³⁺ solutions by -particles are presented. It was found that the radioluminescence intensity of Eu³⁺ ions in both solvents increases proportionally to the energy input by -particles. The yield of radioluminescence photons from europium ions in the POCl₃–SnCl₄–UO²⁺ ₂–Eu³⁺ solutions is more than nine times as high as that in D₂O–UO²⁺ ₂–Eu³⁺. The radiation-chemical yields of excited ⁵ D ₀ states of Eu³⁺ ions are 0.74 ± 0.07 and 0.18 ± 0.02 ions/100 eV in POCl₃–SnCl₄–UO²⁺ ₂–Eu³⁺ and D₂O–UO²⁺ ₂–Eu³⁺ solutions, respectively.     

Extraction separation of rare-earth elements by amines in the presence of complexing agents

The extraction separation of La and Sm by benzyldibutylamine (BDBA) from an aqueous solution containing 6 mol·dm^–3 NaNO₃ and 0.5 mol·dm^–3 HNO₃ is not very efficient. It may remarkably be improved by addition of a complexing agent, 2-hydroxyethylethylenediaminetriacetic acid (HEDTA). The effect of preferential La extraction into the organic phase together with the effect of preferential complexation of Sm in the aqueous phase may lead, by proper choice of the complexing agent concentration, to a 7–10 fold increase in _La/Sm values. The procedure described here enables fairly good separation of a major from minor elements.     

Bimodal normal distribution model for binding of trivalent europium by soil fulvic acid

Complexation of trivalent europium by a well characterized soil fulvic acid was investigated by equilibrium dialysis titration method ([FA]=24 mg·dm^–3, [Eu] _t =9.0·10^–7–3.5·10^–6 mol·dm^–3, pH 6.0). The concentrations of the fulvate bound and free europium were measured radiometrically using¹⁵²Eu as a tracer. The experimental results were evaluated using a bimodal normal distribution model and a plot with two overlapping normal distributions was obtained which gave two means logK (µ_I=7.0, _I=1.1; µ_II=4.9, _II=0.5) values for binding of europium by two classes of sites in fulvic acid. A multiligand model was assumed for fulvic acid, based upon the Eu(III) luminescence studies (⁷F₀⁵D₀ excitation) on many organic acids as model ligands.     

Kinetic Spectrophotometric Determination of Chromium (VI) by Oxidation of Sodium Pyrogallol-5-sulphonate by Hydrogen Peroxide

Summary. A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of chromium (VI). The method is based on the catalytic effect of Cr(VI) on the reaction of sodium pyrogallol-5-sulphonate (PS) with hydrogen peroxide. The reaction is followed spectrophotometrically by tracing the oxidation product at 437nm within 1min after addition of H₂O₂. The optimum reaction conditions are PS (1.32·10^–3mol·dm^–3), H₂O₂ (0.32mol·dm^–3), HClO₄ (2.6·10^–3mol·dm^–3) at 25°C. Following this procedure, chromium (VI) can be determined with a linear calibration graph up to 0.25ng·cm^–3 and a detection limit of 0.024ng·cm^–3, based on the 3 criterion. The interference effect of several species was also investigated and it was found that the most common cations and anions do not interfere with the determination. The developed procedure was successfully applied to the determination of Cr(VI) and total Cr in river waters and total Cr in herbal samples.     

Transport of titanium(IV) ions across di-2-ethylhexylphosphoric acid-CCl4 supported liquid membranes

Transport study for Ti(IV) ions using di-2-ethylhexylphosphoric acid (D2EHPA) (carrier)-CCl₄ (diluent) liquid supported membrane in microporous polypropylene hydrophobic film has been performed. The parameters studied are effects of carrier, H₂SO₄, stripping agent (NH₄F) concentrations and temperature variation on flux and permeability coefficients of the metal ion. The optimum concentrations of transport found are 2.04 mol·dm^–3 D2EHPA, 1.0 mol·dm^–3 H₂SO₄ in the feed and 1 mol·dm^–3 NH₄F as stripping agent. The maximum flux and permeability coefficient determined are 1.32·10^–5 mol·m^–2·s^–1 and 8.02·10^–12 mol·m^–2·s^–1, respectively. The transport of this metal ion is increased with increase in temperature. The mechanism of transport appears to be based on coupled counter ion transport phenomenon.     

A study by pulse radiolysis of the radiation-chemical transformation of aqueous solutions of hydrazine in the presence of oxygen

It is shown by pulse radiolysis that in aqueous solutions of hydrazine containing oxygen the radical N₂H₃ reduces oxygen to O₂ ^– at pH > 7 (k 3·10⁹ dm³· mole^–1·sec^–1), while this reaction does not occur for the protonated form N₂H₄ ⁺ at pH < 7 (k, 5·10⁶ dm³·mole^–1·sec^–1). The rate constants for the disappearance of O₂ ^– have been determined in the pH range from 4 to 12. Rate constants have been calculated for the reaction of O^– with N₂H₄ [k=(1.6 ±0.2)·10⁹ dm³·mole^–1·sec^–1] and of O₃with N₂H₄ [k=(1.2 ±0.2)·10⁶ dm³· mole^–1·sec^–1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 341–345, February, 1991.     

Kinetic Spectrophotometric Determination of Chromium (VI) by Oxidation of Sodium Pyrogallol-5-sulphonate by Hydrogen Peroxide

A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of chromium (VI). The method is based on the catalytic effect of Cr(VI) on the reaction of sodium pyrogallol-5-sulphonate (PS) with hydrogen peroxide. The reaction is followed spectrophotometrically by tracing the oxidation product at 437nm within 1min after addition of H₂O₂. The optimum reaction conditions are PS (1.32·10^–3mol·dm^–3), H₂O₂ (0.32mol·dm^–3), HClO₄ (2.6·10^–3mol·dm^–3) at 25°C. Following this procedure, chromium (VI) can be determined with a linear calibration graph up to 0.25ng·cm^–3 and a detection limit of 0.024ng·cm^–3, based on the 3 criterion. The interference effect of several species was also investigated and it was found that the most common cations and anions do not interfere with the determination. The developed procedure was successfully applied to the determination of Cr(VI) and total Cr in river waters and total Cr in herbal samples.     

Cation exchange selectivity of some fission products on strongly acidic cation exchanger of sulfonic acid type-nitric acid system

Distribution coefficients of fission products in nitric acid for strongly acidic cation exchanger of sulfonic acid type with different cross-linking and structure were measured by a column method. Uptake of cationic fission products increases with resin cross-linking and decreases of nitric acid concentration. The distribution coefficient of the ion, [Kd_Mn+]^*, in a given system is expressed as log [Kd_Mn+]^*=B·log[Kd_Mn+]+A where [Kd_Mn+] is the distribution coefficient of the ion at 1M nitric acid for 10% crosslinked gel type cation exchanger, while A and B constants. Deviation from the above relation were observed for Y³⁺ and complex ions of ruthenium upward for macroporous type cation exchanger and downward for highly porous type cation exchanger. Upward deviation of Y³⁺ for 10% cross-linked gel type cation exchanger increased with concentration of nitric acid. Consequently, elution sequence varied from Y³⁺–Eu³⁺–Pm³⁺–Ce³⁺⁺ at 1M nitric acid to Eu³⁺–Pm³⁺–Y³⁺–Ce³⁺ for the same cation exchanger at 2M nitric acid. The same elution sequence, Eu³⁺–Pm³⁺–Y³⁺–Ce³⁺, was observed for 8% cross-linked gel type cation exchanger and 10% cross-linking macroporous type cation exchanger at 1M nitric acid.     

Precipitation separation of strontium and calcium from acidic solutions using crown ether and tungstosilicic acid

Strontium forms a compound of composition (SrL)₂A·nH₂O with low solubility (5.0·10^–6 mol Sr·dm^–3) in the presence of 18-crown-6 (L) and tungstosilicic acid (H₄A) in acid media, as has been found by radiometric precipitation titration. Formation of the compound with limited solubility was used for separation of strontium and calcium from 1 mol·dm^–3 HCl. It is possible to separate strontium in the range from trace to 6 mmol·dm^–3 in the presence of calcium with its concentration up to 0.2 mol ·dm^–3 and the recovery determined was 95% of Sr and 5% Ca or 90% of Sr and 4% Ca, respectively. The ratio of Sr/Ca depends on the stability constants ratio of metal-L (⊃_SR/⊃_ca) in the case of gradual addition of L. Potassium up to the concentration of 0.05 mol·dm^–3 does not influence recovery of strontium.     

Pulse radiolysis investigations on the reactions of primary radiolytic species of water with atropine

On pulse radiolysis of N₂O saturated aqueous solutions of atropine, an optical absorption band (_max at 320 nm,e=2.81·10³ dm³·mol^–1·cm^–1) was observed, which is assigned to the product of reaction of OH radicals with the solute. This absorption decayed following second order kinetics with a rate constant of 4.5·10⁸ dm³·mol^–1·s^–1. The rate constant for the reaction of OH radicals with atropine as estimated by following the build-up kinetics is 2.7·10⁹ dm³·mol^–1·s^–1. The H atoms also reacted with this compound to produce a transient absorption band behaving similarly to the one observed in the case of reaction with OH radicals. The transient species formed in both cases is assigned to a radical derived by H atom abstraction by H/OH radicals from the parent compound. This radical was unreactive towards 2-mercaptoethanol. e _aq ^– was found to react with atropine forming a transient band with _max at 310 nm (=3.55·10³ dm³·mol^–1). Its decay was also second order with a rate constant of 1.64·10⁹ dm³·mol^–1·s^–1. The bimolecular rate constant for the reaction of e _aq ^– with atropine as estimated from the decay of e _aq ^– absorption at 720 nm is 3.9·10⁹ dm³·mol^–1·s^–1. Specific one-electron oxidizing and reducing agents (such as Cl ₂ ^– , Tl²⁺, SO ₄ ^– and (CH₃)₂COH, CO ₂ ^– , respectively) failed to oxidize or reduce this compound in aqoues solutions. The radical anion of atropine formed by its reaction with e _aq ^– was found to reduce thionine and methyl viologen with bimolecular rate constant of 3.8·10⁹ and 3.2·10⁹ dm³·mol^–1·s^–1, respectively.     

Nitric acid transport across TBP—Kerosene oil supported liquid membranes

HNO₃ transport across tri-n-butyl phosphate kerosene oil supported liquid membrane with or without uranyl ion transport has been studied. Parameters studied are the effect of TBP in the membrane, nitric acid in the feed solution and nitrate ion concentration in the feed solution. The flux of protons for 1 to 10 mol·dm^–3 HNO₃ solution is in the range of (0–25)·10^–4 mol·m^–2·s^–1 and for the TBP concentration range of 0.359 to 3.59 mol·dm^–3, the flux determined is (8.9 to 22)·10^–4 mol·m^–2·s^–1. From the experimental data and using theoretical equations the complex under transport through the membrane appears to be 2TBP·HNO₃ both in the presence and absence of uranyl ions. The diffusion coefficient for H⁺ ions through the membrane as a function of TBP concentration varies from (53 to 6)·10^–12 m²·s^–1, based on experimental flux and permeability data. The values of this coefficient supposing 2TBP·HNO₃ as diffusing species, based on viscosity data and theoretical estimation varies from (82.50 to 3.30)·10^–12 m²·s^–1. The value of distribution coefficient varies in the reverse direction from 0.06 to 1.46 at the same TBP concentration.     

Optical and gamma irradiation studies of morin in ethanol

Spectral studies of morin in aqueous ethanol and other alcohols have been carried out as a function of its concentration and that of ethanol, and the pH of aqueous buffer. The effect of gamma radiations on morin solution in ethanol was also studied as a function of dose in the range of 0.15–2.28 kGy and of morin concentration (10^–5–10^–4 mole·dm^–3). Morin concentration in ethanol solution showed a linear response for G values to a dose of 1.83 kGy. Molar absorption coefficients () for morin in ethanol have been estimated to be _260nm=2.28·10⁴ dm³·mol^–1·cm^–1 and _291nm=8.22·10³ dm³·mol^–1·cm^–1 for unirradiated and _{291 nm}=1.75·10⁴ dm³·mol^–1·cm^–1 for irradiated solutions to a dose of 1.83 kGy.     

Studies on the equilibrium uptake of some metal ions on a mixed and doped hydrous oxide using radiotracers

A highly sensitive and rapid method has been developed for the extraction-spectrophotometric determination of ultra trace amounts of americium. Americium(III) is selectively extracted from 1–10M HNO₃ medium with a mixture of (0.3M HDEHP+0.1M P₂O₅), both dissolved in xylene, and finally estimated in the organic phase itself absorptiometrically employing Arsenazo-III as the chromogenic reagent. A 60% dioxaneethanol mixture was used for optium colour development. Beer's law is obeyed in the concentration range 0.1–0.7 g Am cm^–3 and as little as 0.11 g Am cm^–3 could be determined with a precision better than ±2%. The molar absorptivity based on Am content is (3.599±0.049)·10⁵ dm³·mol^–1·cm^–1 at 648 nm which is incidentally the highest value reported as yet for its determination. The optimum concentration range, evaluated by Ringbom's method is 0.1–0.6 ppm Am. Common contaminants such as Al³⁺, Co²⁺, Cr³⁺, Fe³⁺, Ni²⁺, Zr⁴⁺, F^–, NO₃ ^–, and SO ₄ ^2- in fairly large quantities and moderate amounts of Pu⁴⁺, Th⁴⁺ and UO ₂ ²⁺ cause no interference in the final assay. Colour development is almost instantaneous and its intensity remains virtually constant for at least 48 hours.     

Radiolysis of ground water: Influence of carbonate and chloride on hydrogen peroxide production

Small volumes of aqueous solutions have been subjected to -radiation from a²⁴¹Am source. The irradiated solution was separated from the bulk solution by a glass filter serving as a diffusion barrier. The H₂O₂ concentration in the bulk solution was monitored by a chemiluminescence technique and the overall production of oxidizing species (H₂O₂/O₂) in irradiated ground water was studied by measuring the Fe²⁺-consumption in ground water initially containing 2·10^–6 mol dm^–3 Fe²⁺. H₂O₂ yields calculated using the computer program CHEMSIMUL are in fair agreement with experimental yields for pure water (pH 8) and aqueous methanol solutions (pH 5). Experimentally G(H₂O₂)=1.06±0.1 was obtained in pure water. In solutions containing 2·10^–3 mol·dm^–3 HCO ₃ ^– and in ground water G(H₂O₂) decreased to 0.69±0.03. A corresponding decrease in G(H₂O₂) was not found in the calculations. The agreement between measured and calculated Fe²⁺ consumption is fair when slow oxidative reactions in the bulk solutions are taken into account.     

Kinetics and mechanism of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) ion

Summary The kinetics of the first step of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) [malH^–=HO₂CCH₂CO ₂ ^– ] has been investigated in the 15–35° C range, I=0.3 mol dm^–3 (NaClO₄) and [OH^–]=0.015–0.29 mol dm^–3. The rate law is given by –d In[complex]_T/dt=k₁[OH^–] and at 30° C, k₁=8.5×10^–3 dm³ mol^–1s^–1, H=117.0±7.0 kJ mol^–1 and S=99.0±24.0 JK^–1mol^–1. The activation parameters data are consistent with the SN₁ cb mechanism.     

Sorption of radionuclides on natural materials

Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides⁶⁰Co,¹³⁴Cs and¹³⁷Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm^–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff D_Cs=100 dm³·kg^–1 and the worst results had fly ash D_Cs=4.1 dm³·kg^–1. The best results for cobalt in those solutions had tobermorite D_Co=38 dm³·kg^–1 and the worst results had fly ash D_Co=6.9 dm³·kg^–1.     

Extraction and stripping study of strontium ions across D2EHPA-TBP-kerosene oil based supported liquid membranes

A Sr ion transport study across D2EHPA-TBP kerosene oil based liquid membranes supported on microporous polypropylene film has been performed. The parameters studied were the effect of di(2-ethylhexyl)phosphoric acid (D2EHPA) and TBP concentration variation in the membrane liquid, HNO₃ concentration variation in the stripping phase and citric acid concentration variation in the feed solution. The optimum conditions of transport are 0.3 mol/dm³ D2EHPA, 0.1 mol/dm³ TBP, 0.01 mol/dm³ citric acid in feed and 2 mol/dm³ HNO₃ in the stripping phase. The mechanism of transport observed is counter-ion coupled transport. The coupling ions are protons. The maximum flux for Sr ion transport observed is 5.33·10^–5 mol·m^–2·s^–1 and maximum permeability under optimum conditions observed is 8.08·10^–11 m^–2·s^–1.     

The aggregation in dodecyltrimethylammonium hydroxide aqueous solutions

The aggregation of dodecyltrimethylammonium hydroxide (DTAOH) aqueous solutions has been studied by several methods. It is stepwise and four critical points were found. AtC _T=(2.51±0.10)×10^–4 mol · dm^–3 the surface excess becomes zero, atC _T=(1.300±0.041)×10^–3 mol · dm^–3 small aggregates from, which grow with concentration. AtC _T=(1.108±0.010)×10^–2 mol · dm^–3 true micelles form (CMC) and at (3.02±0.28)×10^–2 mol · dm^–3 the structure of micelles probably changes affecting their properties. The DTAOH micelles are highly ionized (=0.8) at the CMC, and decreases to reach very small values when the total concentration increases.